A flat panel display, such as liquid crystal display (LCD), organic electro-luminescent display (OELD) or liquid crystal on silicon (LCOS), plays an important role as a communication interface between people and the information in the modern living. The flat panel display is assembled using a first and a second substrate. Before assembling, one or several contact pads for positioning conductive drops (for example, Au drop or Ag drop) are formed at one of the substrates (for example, substrate having thin film transistors (TFT) or organic electro-luminescent diodes, or silicon substrate). After completing the assembly of the second substrate and the first substrate, the substrates are electrically connected through the contact pads and the conductive drops.
In general, the flat panel display comprises two substrates. One substrate comprises several electronic components (i.e. switches, transistors, diodes, capacitors, etc.), electrodes and conductive lines, and the other substrate comprises electrodes, conductive lines or a color filter (CF). An example of a flat panel display is a Thin Film Transistor-Liquid Crystal Display (TFT-LCD), which comprises a first substrate, a second substrate and a Liquid Crystal (LC) medium (i.e. numerous LC molecules) therebetween. The first substrate (such as a transparent glass) comprises thin film transistors (TFTs) arranged in an array, pixel electrodes, orthogonal scan (gate) lines and data (signal) lines. The second substrate (such as a transparent glass) comprises the CFs. In the traditional method of fabricating the Liquid Crystal Display (LCD), the second substrate having CFs and sealant is aligned and pressed with the first substrate having TFTs. The sealant is then cured for assembling the second substrate and the first substrate. For small size display, the cell (i.e. space between the substrates) is a vacuum, which is created by capillary attraction after two substrates are assembled. But for large size display, the newly developed method, call “one drop fill” (ODF), is to drop the LC directly on the substrate before the two substrates are aligned and assembled.
Whether a large size display or a small-sized-display is manufactured, one or several contact pads are formed at one (for example, the lower substrate having TFT) of the substrates for positioning conductive drops (i.e. Au drops or Ag drops) before the substrates are assembled. Referring to FIG. 1, a conventional panel having the contact pads is illustrated. Also, FIG. 1 illustrates a small size (ex: 1.79″) panel. Two contact pads 102, 104, which are made from a conductive material, are positioned at the corners of a panel 100. The two contact pads 102 and 104 are coincident with the bonding positions of conductive drops.
However, the conductive drops could miss the positions of the contact pads, due to the misdrop by a machine or other factors. Applying the conductive drops to a position other than the contact pads 102 and 104 results in an electrical-connection flaw on the display, which is typically noticed after assembly of the substrates. The conventional design of the contact pad cannot prevent or test whether the conductive drops miss the positions of the contact pads.